Ceramic matrix composites (CMC) are often used in applications requiring high strength in elevated temperature environments, such as turbine engine components, including turbine blades.
Generally, such turbine components require attachment to adjoining metallic hardware and/or metallic surfaces, sometimes referred to as disks. Among disadvantages associated with attaching a CMC to metallic hardware is the wear of the metallic hardware by the hard, abrasive ceramic material surface. Debris generated as a result of wear, when trapped between CMC and metallic hardware surfaces, acts to accelerate the wear between the CMC and metallic components. Under high contact stresses, damage to the ceramic material surface is also possible, usually due to matrix cracking and fiber breakage that lead to the formation of wear troughs.
In response, U.S. Publication No. U.S. 2010/0284816 discloses a method for creating a fir tree dovetail attachment for a CMC airfoil using a secondary metallic member with multiple contact surfaces. The metallic member is intended to trap the CMC and transfer the airfoil loading into the metallic member which has features/bearing surfaces similar to a multi-tooth fir tree attachment. These surfaces are designed for load transfer and not to reduce friction or wear at the disk attachment interface. Design against wear is not discussed.
U.S. Pat. No. 5,466,979 discloses use of a vibration source with a tailored frequency to help remove debris particles that build-up on the contact surface in an effort to lessen wear rates.
EP Publication No. 0 352 476 discloses incorporating a circumferential internal wear pocket and radial slots, but for purposes of reducing forced excitation due to fluid flow.
What is needed is an apparatus or method of manufacturing CMC turbine engine components that provides engineered surface features for reducing wear between CMC-to-metal surfaces by substantially removing or otherwise substantially preventing debris from remaining in contact between interfacing CMC-to-metal surfaces.